Athletes have commonly found that training with increased weight around the legs and feet can prove advantageous in improving strength and endurance. In particular, by training with increased weight at the lower extremities of the leg, the athlete can specifically develop muscles for running, jumping, and the like. Non-athletes can also benefit from such leg weighting by incorporating the increased resistance into their daily regimen of walking and moving about. Consequently, such non-athletes might increase their metabolic rate and lose weight. Also, rehabilitative efforts might be hastened and improved with specific weighting.
The prior art provides several approaches towards adding weighting to the foot. Conventional ankle weights are known for use in training and consist of strapable weights applied above the foot, around the ball joint of the ankle. A related approach is disclosed in U.S. Pat. Nos. 3,114,982, 4,458,432, and 4,777,743 which incorporate weighted pouches and/or straps around the top and/or sides of an athletic or sport shoe, near the ankle joint. One of the drawbacks of such side or ankle weights is that the length of the moment arm about (or around) the ankle pivot is generally zero. As a result, muscle groups associated with rotating the foot are not fully or properly developed with such side or ankle weights. Instead, only the leg muscles for lifting the foot are developed.
U.S. Pat. No. 1,990,970 discloses an exercising shoe which straps onto the bottom of the foot and has interchangable weight plates. The weight plates are held in place via coil springs and bolts. This strap-on device does not provide a practical or aesthetic device which can be utilized during everyday activities. Moreover, this device supplants the benefits and comfort of the shoe's natural sole.
U.S. Pat. No. 5,231,776 discloses an integrally weighted athletic shoe wherein the weight is distributed over the entire bottom, but inside the shoe. The weight is comprised of a large number of metal spheres arranged in a lattice grid network and permanently manufactured between the inner and outer sole of the shoe. Since the weight is permanently fixed into the finished shoe, this device does not allow for customization of a particular pair of shoes as an athlete needs change. Instead, the shoe needs to be physically opened up and modified, or the shoe needs to be replaced.
U.S. Pat. No. 3,517,928 discloses a weighted shoe which uses a weight-receiving member frame inside the shoe which is coextensive with the sole. The weight-receiving frame is permanently built into the shoe and has openings for receiving different weight plugs. The disadvantage of this device is that a favorite or expensive shoe would need be permanently altered to properly incorporate the member frame according to the disclosure.
Accordingly, what is needed in the art is an apparatus for adding weight to any shoe in a comfortable and yet aesthetically pleasing manner. This device would include a flexible insole which is weighted and sized according to a user's needs. An ideal material for such an insole would be a rubberized compound with any weight sealably contained therein for comfort and durability. The weights should be placed within the rubber underneath the user's foot so as to maximize comfort. A series of anti-slip nodes might also be provided on the bottom surface of the insole to interface with the bottom material on the inside of the shoe.